The present invention is directed to one-way clutches and, more particularly, to a bicycle roller clutch used for transmitting force to a bicycle wheel.
A one-way rotation clutch comprising a roller or pawl system has been used for the freewheels of the drive-side wheels on bicycles. As shown in FIG. 5, a known roller clutch 30 has a plurality of rollers 31 which are fitted into and supported by roller supports 32 so that they are in rolling contact around the outside surface of a cone 33. A cup 35 has grooves 36, whose radius increases circumferentially in a successive and linear fashion in a drive direction of the clutch (indicated by an arrow). Clutch 30 is designed such that each individual roller 31 is biased by a compressed coil spring 34 fixed to a roller support 32 toward the narrow side of the groove 36. When the clutch rotates in the drive direction, the rollers 31 move further into the narrow side of the grooves 36 so that the frictional force between the rollers 31, the cone 33 and the cup 35 cause the cone 31 and the cup 35 to rotate as a unit. When driving force is released, the rollers 31 move toward the wider side of the grooves 36, thus allowing the cone 33 and the cup 35 to rotate relative to each other (known as freewheeling).
An advantage of a roller clutch system such as this is that a secure lock can be achieved even if there are dimensional errors in the rollers, dimensional errors in the cup grooves, or dimensional errors in the cone. Furthermore, the noise inherent in traditional pawl clutch arrangements is eliminated. However, there is a disadvantage in that the biasing force of the springs 34 must be large in order to provide quick operation of the clutch. This large biasing force causes added friction between the rollers 31, the cone 33 and the cup 35 to cause an increase in torque during freewheeling when the cup 35 is unloaded. This, in turn, causes an undesirable dragging action on the chain and increasing wear on the components.